Undefined Reference Error

I am getting an Undefined reference to <function>, here is my code:

Code:

`#include <stdio.h>`

#include "qsolver.h"

int main() {

double a, b, c, x1, x2;

int qret;

while(1) {

printf("Enter variables for quadratic equation (type: \n");

scanf("%lf %lf %lf", &a, &b, &c);

if((qret = qsolver(a, b, c, &x1, &x2)) != 0) {

printf("Error Value: %d\n", qret);

}

}

return 0;

}

******************************************************************************

#include <stdio.h>

#include <math.h>

#include "qsolver.h"

int qsolver(double a, double b, double c, double* x1, double* x2) {

//Is the user giving an input which would divide by zero?

if(a == 0) {

printf("Input Not A Quadratic; Cannot Have Value Of '0' For A\n");

return 1;

}

//Is the user giving and input which would try to compute a square root of a negative number.

else if( (4*a*c) > pow(b,2) ) {

printf("There Are No Real Solutions; B^2 Is Less Than (4*A*C)\n");

return 2;

}

//The user input is valid, solve accordingly

else {

*x1 = (-b + sqrt(pow(b,2) - (4*a*c)))/(2*a);

*x2 = (-b - sqrt(pow(b,2) - (4*a*c)))/(2*a);

return 0;

}

}

*****************************************************************************************

#ifndef QSOLVER_H

#define QSOLVER_H

int qsolver(double, double, double, double *, double *);

#endif